Natural radiation comes from terrestrial background i.e., soils and rocks and the building materials derived from them. The decay of naturally occurring radionuclides in soil produces alpha, beta and gamma radiation field in soil that also crosses the soil-air interface to produce exposure to humans. Natural radionuclides in a river environment can generate a significant component of the background radiation exposure to the population. Therefore, the knowledge of the concentrations and distributions of the natural radionuclides in the river environment is of great interest, since it provides useful information in the monitoring of environmental contamination and associated human health by natural radioactivity. In view of that, in the book contains the systematic investigations were carried out to understand the distribution and transport of radionuclide in the riverine environs of the major rivers of South Karnataka India, namely Hemavathi and Cauvery.